Highway crossing signal control system



April 11, 1944. 'r. w. TIZZARD, JR

HIGHWAY CROSSING SIGNAL CONTROL SYSTEM File Oct. 7, 1942 Patented Apr.11, 1944 HIGHWAY CROSSING SIGNAL CONTROL SYSTEM Thomas W. Tizzard, Jr.,Downers Grove, 111., assignor to The Union Switch and Signal Company,Swissvalc, Pa., a corporation of Pennsylvam'a Application October 7,1942, Serial No. 461,102

2 Claims.

My invention relates to apparatus for controlling highway crossingsignals, that is, to apparatus for the control of signals which areplaced at the intersection of a highway and a stretch of railroad trackto warn users of the highway of the approach of a train.

An object of my invention is to provide improved means for discontinuingoperation of a crossing signal in the event that a train should stopwithin a control section for such signa1 before it reaches the crossing.

A further object of the invention is to provide an improved system ofthe type described and incorporating means to initiate operation of thecrossing signals when a train which has stopped in the control sectionagain advances towards the intersection.

Other objects of the invention and features of novelty will be apparentfrom the following description taken in connection with the accompanyingdrawing.

I shall describe one form of highway crossing signal control systemembodying my invention, and shall then point out the novel featuresthereof in claims.

, In the drawing the single figure is a diagram of a stretch of railwaytrack equipped with one form of apparatus embodying my invention.

In practicing my invention I provide an approach track section at oneside of the intersection and equip this section with track circuitapparatus including a principal track relay at the end of the sectionremote from the intersection. An insulated joint is installed in onetrack rail of theapproach section to divide the section into a timingportion remote from the intersection and a "restart portion adjacent theintersection. An auxiliary track relay is connected around thisinsulated joint so as to be included in series with the principal trackrelay. The principal and auxiliary track relays cooperate to control thecrossing signal control relay, and also cooperate to control a timingrelay which operates to discontinue operation of the crossing signals ifa train remains in the timing portion of the approach section for longerthan a predetermined time. The equipment is also arranged so that assoon as a train enters the restart portion of the section, operation ofthe crossing signals will be initiated and will be continued as long asa train remains in that portion of the section.

Referring to the drawing, there is shown therein a stretch of railwaytrack over which trailic normally moves in the direction indicated bythe arrow, that is, from left to right. The track stretch is intersectedat grade by a highway, while crossing signals XS of any suitable formare provided to warn users of the highway of the approach of a train.Insulated joints 3 are placed in the track rails l and 2 to form anapproach track section for the control of the crossing signals, while aninsulated joint 4 is placed in track rail 2 to divide the approach.section into a timing portion remote from the intersection and a"restart portion adjacent the intersection.

The approach section is of such length that if operation of the crossingsignal is initiated when a train enters the section, the signals will beoperated for at least a predetermined time, such as 30 seconds, beforethe train reaches the intersection even through the train is travelingat ahigh rate of speed.

The "timing portion of the approach section is of such length that atrain moving at any substantial speed will pass through this portion inless than the pick-up time of a slow pick-up relay TER. The restartportion of the approach section is of such length that a train whichstopped in the timing portion of the section, or which traveled soslowly through that portion as not to pass through it before the relayTER. picks up, will not traverse the "restart portion and reach theintersection until after the expiration of a suitable time interval,such as 30 seconds, so that if operation of the signals was discontinueddue to occupation of the timing portion, and the crossing signals arestarted when a train enters the "restart portion, they will be operatedfor an appropriate time interval before the train reaches theintersection, and users of the highway will have adequate warning of theapproach of the train.

The approach section is provided with track circuit apparatus includinga track battery which is connected across the section rails at the endof the section adjacent the intersection, and a principal track relay TRwhich is connected across 101 of any suitable construction and isarranged so that on the supply of energy to the relay winding itscontacts become picked up after the expiration of a predetermined timeinterval, such as 30 seconds, while the relay contacts thereafterremainpicked up as long as energy is supplied to the relay winding, butrelease promptly when the supply of energy to the relay winding isinterrupted. The construction of the relay TER is not a part of thisinvention; one form of relay which I may employ is shown in LettersPatent of the United States No. 1,966,965, issued July 1'7, 1934, t'oBranko Lazich and Harry E. Ashworth.

The relays TER and XR, and the crossing signals XS are supplied withenergy from a suitable source of current, such as a storage battery, notshown, the terminals of which are designated B and C in the drawing.

The equipment is shown in the condition which it assumes when the trackstretch is vacant. At this time the principal track relay '1?) is energi'z'ed by current supplied from the track battery over the sectionrails and through the winding of the auxiliary track relay TRA.Accordingly, the contacts of relay TR are picked up, while as explainedabove,'too little energy flows through the winding of relay 'I'RA topick up its contacts so the contacts of relay TRA are released.

Under these conditions the circuit of relay TER is interrupted and itscontacts are released so energy isjsup'pli'ed to relay XR over thecircuit which is' traced from terminal B through front contact id ofrelay TR, back contact ll of relay TRA, back contact !2 of relay TER,and winding of relay XR to terminal 0. Accordingly, contact It of relayXR is picked up and interrupts the circuit of the crossing signals XS toprevent operation of these signals at this time.

When a train moving in the normal direction of trafiic enters'theapproach section, the principal track relay TR is shunted and. itscontact it releases and interrupts the circuit of relay XR so contact Mof relay XR releases and establishes the circuit of the crossing signalsXS so that they operate to warn users of the highway of the approach ofa train.

In addition, on entrance of a train into the approach section withresultant shunting of the track relay TR there is an increase in currentflowing in the track circuit and in the winding of the auxiliarytrackrelay TRA, andthe contacts of this relay pick up so that contact lladditionally interrupts the circuit of the relay XR, while contact E ofrelay TRA establishes a circuit including back contact Id of relay TRfor supplying energy to the slow pick-up relay TER.

If the train is traveling at a substantial speed, it. will'advancebeyond the insulated joint 4 before the contacts of the relay TER becomepicked up. When the train advances beyond the insulated joint i andenters the restart'portion of the approach section, the auxiliary trackrelay TRA is shunted and its contacts release so that contact l5interrupts the circuit of relay TER and the contacts of relay TER remainreleased, while the circuit of relay XR continues to be interrupted bycontact ll] of relay TR so contact M of relay XR maintains the circuitof the crossing signals XS and these continue to operate to warn usersof the highway of the approach of} the train.

When the train vacates the approach section, energy from the trackbattery again feeds to the relay TR and its contact lfli picks up andestablishes the circuit traced above for supplying energy to the relayXR so that its contact 14 picks up and discontinues operation of thecrossing signals.

As pointed out above, when a train moving in the normal direction oftrafiic enters the approach section, the relay TR releases and itscontact In interrupts the circuit of relay XR to thereby initiateoperation of the crossing signals XS, while relay TRA picks up so energyis supplied to relay TER. over back contact [0 of relay TR and frontcontact lb of relay TRA.

After a time interval, the contacts of relay TER become picked up andcontact H5 establishes a circuit including front contact llof relay TRAto supply energy to relay XR so that its contact M is picked up todiscontinue operation of the crossing signals. As long as the trainremains in the timing portion of the approach section and does notadvance into the restart portion of this section, the contacts of relayTRA remain picked up so energy continues to be supplied to the relay TERand its contacts will remain picked up and maintain the circuit forsupplying energy to relay 2m and contact I4 of relay XR is picked up toprevent operation of the crossing signals. This is advantageous as itprevents operation of the crossing signals at a time when a train isnotapproaching the intersection. This eliminates unnecessary delay of usersof the highway and helps to prevent disregard of the crossing signals byusers of the highway.

When the train which stopped in the timing" portion of the approachsection advances beyond the insulated joint 4 and enters the restart"portion of the approach section, the auxiliary track r'elay'TRAis'shunted and its contacts release with the result that its contact I!interruptsthe circuit of the relay XR so that contact l4 releases andestablishes the circuit of the crossing signals XS and they operate towarn users of the highway of the approach of the train.

In addition, on release of relay TRA its contact I5 interrupts thecircuit of the relay TER sothe contacts of relay TER release and itscontact It additionally interrupts the circuit of the relay XR.

As pointed out above, the insulated joint 4 is located far enough fromthe intersection to insure that after a train which stopped beforereaching the joint, or traveled so slowly through the timing portion ofthe approach section that the relay TER became picked up before thetrain reachedthe joint 4, a predetermined time interval will elapsebefore the train reaches the intersection. This insures that users ofthe highway will have adequate warning of the approach of trains whichstop in the timing section and subsequently start up again.

This system is arranged so that a back contact I! ofthe auxiliary trackrelay TRA is included in the circuit for supplying energy to the relay.XRL'wheri the'contacts of the relay TR are picked up. Accordingly, iffor any reason, such as changes in ballast conditions, track batteryvoltage or the like, the auxiliary track relay TRA should be picked upat a time when the timing portion of the approach section is vacant, therelay XR will be released and the crossing signals will operatecontinuously. This operation of the signals will provide an indicationthat the equipment is not functioning as intended, and the signalmaintainer can thereupon change the adjustment of the track circuit toprevent picking up of the relay TRA while the approach section isvacant.

In addition, it will be seen that if the auxiliary track relay TBA ispicked up when the approach section is vacant, energy will not besupplied to the timing relay TER since the circuit of relay TER includesback contact ill of relay TR. Accordingly, if the auxiliary track relayTRA is picked up when the principal track relay TR is picked up, thetiming relay TER will not pick up, but will remain released and will notestablish the circuit controlled thereby for supplying energy to therelay XR.

Although I have illustrated and described only one form of highwaycrossing signal control system embodying my invention, it is understoodthat various changes and modifications may be made therein within thescope of the appended claims without departing from the spirit and scopeof my invention.

Having thus described my invention, what I claim is:

1. In combination, a stretch of railway track intersected by a highway,a highway crossing signal located at the crossing, a control relayeffective when energized to prevent operation of said signal, the railsof said track stretch being divided by insulated joints into an approachsection which is traversed by a train approaching said crossing, asource of energy connected across the approach section rails at the endof the section adjacent the crossing, a principal track relay connectedacross the approach section rails at the end of the section remote fromthe crossing, an auxiliary track relay connected in series with one ofthe rails of the approach section at an intermediate point in saidsection, the track relays and the source of energy being proportioned sothat when the approach section is vacant the principal track relay ispicked up and the auxiliary track relay is released and so that onentrance into the section of a train approaching the crossing theauxiliary track relay picks up and remains picked up until the trainadvances beyond said auxiliary relay, a timing relay having a normallyopen contact which on the supply of energy to the relay winding becomesclosed only after the expiration of a predetermined time interval, acircuit including a front contact of said principal track relay and aback contact of said auxiliary track relay for supplying energy to saidcontrol relay, a circuit including a back contact of said principaltrack relay and a front contact of said auxiliary track relay forsupplying energy to said timing relay, and a circuit including saidtiming relay contact for supplying energy to said control relay.

2. In combination, a stretch of railway track intersected by a highway,a highway crossing signal located at the crossing, a control relayefiective when energized to prevent operation of said signal, the railsof said track stretch being divided by insulated joints into an approachsection which is traversed by a train approaching said crossing, asource of energy connected across the approach section rails at the endof the section adjacent the crossing, a principal track relay connectedacross the approach section rails at the end of the section remote fromthe crossing, an auxiliary track relay connected in series with one ofthe rails of the approach section at an intermediate point in saidsection, the track relays and the source of energy being proportioned sothat when the approach section is vacant the principal track relay ispicked up and the auxiliary track relay is released and so that onentrance into the section of a train approaching the crossing theauxiliary track relay picks up and remains picked up until the trainadvances beyond said auxiliary relay, a timing relay having a normallyopen contact which on the supply of energy to the relay winding becomesclosed only after the expiration of a predetermined time interval, acircuit including a front contact of said principal track relay and aback contact of said auxiliary track relay for supplying energy to saidcontrol relay, a circuit including a back contact of said principaltrack relay and a front contact of said auxiliary track relay forsupplying energy to said timing relay, and a circuit including a frontcontact of said auxiliary track relay and said timing relay contact forsupplying energy to said control relay.

THOMAS W. TIZZARD, JR.

